The needs of industrial markets for semiconductor devices having characteristics of multi-functions, high-speed operation and low-power consumption have strongly increased. With such needs, among packaged semiconductor devices, a Ball Grid Array (BGA) type which implements a high pin count by forming a plurality of external terminals having a ball shape at a lower surface of a body portion thereof has been favored, rather than a Quad Flat Package (QFP) type which has external terminals protruding toward the outside from side surfaces of the body portion.
Semiconductor devices that have undergone complicated processing are subjected to various types of electrical tests so as to test their characteristics and for defects thereof. To this end, a test socket is used to electrically connect metallic wires or contact pads of a test board (a printed circuit board) mounted in test equipment and external terminals of a device to be tested (a semiconductor package). That is, when testing a semiconductor device, the socket serves as an interface to electrically connect the printed circuit of the test equipment and the semiconductor device under test.
As a trend is driving the BGA type package, test equipment for testing the electrical characteristics of a package is also changing in respect of an appropriate type thereof. For instance, various types of sockets which are electrically connected to the test equipment and capable of being detachably mounted to a package to be tested have been developed and proposed.
FIG. 1 is a longitudinal cross-sectional view of an exemplary related art socket for testing semiconductor package, showing that a pogo pin is used to connect external terminals of a semiconductor package and metal wiring on a printed circuit board (PCB).
Referring to FIG. 1, the related art socket 20 for testing the semiconductor package includes pogo pins 6 for electrically connecting external terminals 3a of a device to be tested (semiconductor package) and contact pads 5a of a test board 5, and a main body 1 having insulating properties and disposing the pogo pins at predetermined intervals to fix and support the pogo pins to protect against deformation and external physical impact.
The pogo pins 6 include pipe-shaped pin bodies 11, metallic upper contactors 12 coupled to an upper end of the pin bodies 11 and contacting external terminals 3a of the package 3, metallic lower contactors 13 coupled to a lower end of the pin bodies 11 and contacting the contact pads 5a of the test board 5, and coil springs 14 disposed inside the pin bodies 11 so that upper ends make contact with the upper contactors 12 and their lower ends contact with the lower contactors 13, and upon testing, making elastic contacts when the upper contactors 12 contact the external terminals 3a of the package 3 and the lower contactors 13 contact the contact pads 5a of the test board 5.
With these configurations, when the related art semiconductor package testing socket 20 is used to test a semiconductor package, a cover (not shown) of the socket 20 is opened, then the package 3 desired to be tested is mounted inside of a package mounting portion 4 formed in a front surface of the main body 1 of the socket, and then the cover (not shown) is closed. Then, external terminals 3a of the package mounted in the package mounting portion 4, the pogo pins 6 and the contact pads 5a of the test board are contacted to each other, thereby establishing electrical connections therebetween. In this state, tests of electrical characteristics are performed.
However, this related art socket 20 electrically connected by the pogo pins 6 has too many contacts, when testing, where electrical contacts are made between the external terminals 3a of the package and the contact pads 5a of the test board, such as between the external terminals 3a of the package and the upper ends of the upper contactors 12 of the pogo pins, between the lower ends of the upper contactors 12 and the upper ends of the coil springs 14, between the lower ends of the coil springs 14 and the upper ends of the lower contactors 13, and between the lower ends of the lower contactors 13 and the contact pads 5a of the test board. Accordingly, the presence of so many contacts causes unstable impedance and poor high frequency characteristics, thereby reducing the reliability of the test.
In order to solve this problem, in Korean Patent No. 555713, the present applicant disclosed a pogo pin in which a cylindrical metallic body having a hollow inner space therein and a spring structure being cut in a screw thread shape (spiral shape) at least partially on an outer surface of a central portion of the body are integrally formed. When this pogo pin is applied to the socket for testing a semiconductor package shown in FIG. 1, contacts exist only between the external terminals of the package and the upper ends of the pogo pins, and between the lower ends of the pogo pins and the contact pads of the test board. Accordingly, this could result in remarkable reduction in erroneous contacts.
However, the pogo pin disclosed in Korean Patent No. 555713 has implemented a spring structure by spirally cutting a portion of an outer surface of a central portion of the body. Accordingly, mechanical properties such as rigidity, and the like are deteriorated. When the pogo pin is repeatedly used, the original shape of the pogo pin is deformed, thereby causing a problem of loose contact.
Further, since the outer surface portion of the body is spirally cut, the path between the external terminals of the package and the contact pads of the test board becomes long, thereby increasing electric resistance.